GHCi doesn't qualify types anymore

M.hs contains:

module M where

import qualified Prelude as P

f n = n P.+ 1

g h (P.Just x) = P.Just (h x)
g _ P.Nothing  = P.Nothing

GHC 7.10.3 behaves as expected:

$ ghci-7.10.3 -ignore-dot-ghci M.hs 
GHCi, version 7.10.3: http://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling M                ( M.hs, interpreted )
Ok, modules loaded: M.
*M> :browse
f :: P.Num a => a -> a
g :: (t -> a) -> P.Maybe t -> P.Maybe a
*M> :t f
f :: P.Num a => a -> a
*M> :t g
g :: (t -> a) -> P.Maybe t -> P.Maybe a

However, GHC HEAD drops the module qualifiers

$ ghci-7.11.20151209 -ignore-dot-ghci M.hs
GHCi, version 7.11.20151209: http://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling M                ( M.hs, interpreted )
Ok, modules loaded: M.
*M> :browse
f :: Num a => a -> a
g :: (t -> a) -> Maybe t -> Maybe a
*M> :t f
f :: Num a => a -> a
*M> :t g
g :: (t -> a) -> Maybe t -> Maybe a
*M> Nothing :: Maybe ()

<interactive>:4:12: error:
    Not in scope: type constructor or class ‘Maybe’
    Perhaps you meant ‘P.Maybe’ (imported from Prelude)

Trac metadata

Trac field	Value
Version	7.11
Type	Bug
TypeOfFailure	OtherFailure
Priority	highest
Resolution	Unresolved
Component	GHCi
Test case
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BlockedBy
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CC	bgamari
Operating system
Architecture